It is well known to catalyze the alkylation of aromatics with a variety of Lewis or Bronsted acid catalysts. Typical commercial catalysts include phosphoric acid/kieselguhr, aluminum halides, boron trifluoride, antimony chloride, stannic chloride, zinc chloride, onium poly(hydrogen fluoride), and hydrogen fluoride. Alkylation with lower molecular weight olefins, such as propylene, can be carried out in the liquid or vapor phase. For alkylations with higher olefins, such as C.sub.16+ olefins, the alkylations are done in the liquid phase, usually in the presence of hydrogen fluoride. Alkylation of benzene with higher olefins is especially difficult, and requires hydrogen fluoride treatment. Such a process is disclosed by Himes in U.S. Pat. No. 4,503,277, entitled "HF Regeneration in Aromatic Hydrocarbon Alkylation Process," which is hereby incorporated by reference for all purposes. However, hydrogen fluoride is not environmentally attractive.
The use of these acids is extremely corrosive, thus requiring special handling and equipment. Also, the use of these acids might involve environmental problems. Another problem is that the use of these acids gives less than desirable control on the precise chemical composition of the product produced. Thus, it would be preferable to use a safer, simpler catalyst, preferably in solid state. This simpler process would result in less capital investment, which would result in a less expensive product.
The alkylates (alkyl aromatic hydrocarbons) typically produced by the catalytic alkylation of aromatics with Normal Alpha Olefins (NAO's) can be characterized by the following three chemical aspects of the alkylate:
1) the "2-aryl" content, PA1 2) the "heavy alkylate" content, and PA1 3) the "branching" content. PA1 (a) mono-alkylate of oligomerized olefins, PA1 (b) di-alkylated species, and PA1 (c) oligomerized olefin species. PA1 (a) less than 40 wt. % of the alkylated aromatic hydrocarbon is characterized by having 2-aryl attachment; PA1 (b) at least 20 wt. % of the alkylated aromatic hydrocarbon is a monoalkylate; and PA1 (c) no more than 90% of the alkyl groups are branched.
The "2-aryl content" is defined as the percentage of total mono-alkylate (the alkylate species in which one alkyl chain is attached to the aromatic ring) that is comprised of those chemical species in which the attachment of the alkyl chain to the aromatic ring is at the 2-position along the alkyl chain.
The "heavy alkylate" is defined as the percentage of the total alkylate that is comprised of those chemical species present with molecular weights higher than that of the mono-alkylate. These chemical species with molecular weights higher than that of the "mono-alkylate" may be composed of, but are not limited, to:
The "branching content" is defined as the percentage of the total mono-alkylate that is composed of chemical species in which the alkyl chain attached to the aromatic ring is not a simple straight chain or normal alkyl group, but those in which alkyl groups (such as methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, isobutyl, and the various hexyl, heptyl and octyl isomers) are attached somewhere along the otherwise normal alkyl chain.
These three parameters are known to impart different properties to the corresponding sulfonates: Neutral, Low Overbased (LOB), or High Overbased (HOB). Thus, a process that allows one to control these three parameters simultaneously in a single process is tremendously advantageous from an efficiency standpoint in the production of alkylates.
For example, the "2-aryl" content is known to influence the performance of the corresponding sulfonate prepared from the alkylate in the area of laundry detergents B. V. Vora, P. R. Pujado, T. Imai, T. R. Fritsch, paper presented in "Recent Advances in the Detergent Industry," Society of Chemical Industry, University of Cambridge, England, Mar. 26-28 (1990)!. Most solid acids produce high 2-aryl attachment when alkylating .alpha.-olefins. See S. Sivasanker, A. Thangaraj, "Distribution of Isomers in the Alkylation of Benzene with Long-Chain Olefins over Solid Acid Catalysts," Journal of Catalysis, 138, 368-390 (1992)!. This is especially true for zeolite Y.
The "heavy alkylate" content is known to influence neutral sulfonates (U.S. Pat. Nos. 3,764,533 and 4,259,193) and overbased sulfonates and both neutral and HOB sulfonates (U.S. Pat. No. 5,112,506). Also, for applications where it is desired to have an alkylate with high "heavy content," being able to control the "heavy content" during the alkylation step has advantages over distilling the alkylate to obtain the desired molecular weight (U.S. Pat. No. 3,288,716). In U.S. Pat. No. 5,112,506, the effect of molecular weight distribution or "heavy alkylate" is shown to influence the performance of both neutral and HOB sulfonates and the dialkylate content is shown to influence the rust performance of the corresponding sulfonate in U.S. Pat. No. 3,764,533. In U.S. Pat. No. 4,259,193, a monoalkylate sulfonate is preferred. U.S. Pat. Nos. 3,288,716; 3,764,533; 4,259,193; and 5,112,506 are hereby incorporated by reference for all purposes.
The "branching" content is known to influence the performance of some sulfonates. In French Patent 2,381, 026 and European Patent 0,001,318, the linear olefin content, relative the branched olefin content, is shown to affect the foaming properties of a sulfonate. In these patents, they obtained the mixtures of the branched and linear alkylates by making physical blends of the two.